全文获取类型
收费全文 | 3327篇 |
免费 | 285篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 24篇 |
综合类 | 5篇 |
化学工业 | 1277篇 |
金属工艺 | 49篇 |
机械仪表 | 89篇 |
建筑科学 | 95篇 |
矿业工程 | 7篇 |
能源动力 | 77篇 |
轻工业 | 661篇 |
水利工程 | 41篇 |
石油天然气 | 25篇 |
无线电 | 172篇 |
一般工业技术 | 489篇 |
冶金工业 | 176篇 |
原子能技术 | 19篇 |
自动化技术 | 409篇 |
出版年
2024年 | 12篇 |
2023年 | 47篇 |
2022年 | 239篇 |
2021年 | 263篇 |
2020年 | 115篇 |
2019年 | 147篇 |
2018年 | 126篇 |
2017年 | 134篇 |
2016年 | 163篇 |
2015年 | 126篇 |
2014年 | 168篇 |
2013年 | 272篇 |
2012年 | 217篇 |
2011年 | 225篇 |
2010年 | 164篇 |
2009年 | 182篇 |
2008年 | 172篇 |
2007年 | 118篇 |
2006年 | 101篇 |
2005年 | 84篇 |
2004年 | 65篇 |
2003年 | 54篇 |
2002年 | 55篇 |
2001年 | 36篇 |
2000年 | 25篇 |
1999年 | 20篇 |
1998年 | 47篇 |
1997年 | 37篇 |
1996年 | 39篇 |
1995年 | 23篇 |
1994年 | 13篇 |
1993年 | 16篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 13篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1982年 | 3篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1973年 | 2篇 |
1968年 | 3篇 |
1967年 | 3篇 |
排序方式: 共有3615条查询结果,搜索用时 31 毫秒
121.
122.
Daniela Bortoluzzi Larissa Rodrigues 《Mineral Processing and Extractive Metallurgy Review》2013,34(4):202-209
This article deals with the study of the vitrification mechanism as an inertization method for coal ashes contaminated with heavy metals. Ashes from coal (thermoelectric) and wastes from mining of fluorite and feldspar and from plating were used to compose vitreous systems using a mixture design. The chemical composition of the wastes was determined by XRF and the formulations were melted at 1450°C for 2 h using 10% (mass) of Na2CO3 (as a fluxing agent). The glasses were poured into a mold and annealed (600°C). The characteristic temperatures were determined by thermal analysis (DTA, air, 20°C/min) and the mechanical behavior by HV. As a result, the softening temperature is strongly dependent on silica content of each glass, and the fluorite residue, being composed mainly by silica, strongly affects on the glass transition (Tg) and softening (Ts) temperatures. The hardness by micro-indentation of all glasses is mainly affected by the plating (galvanic) residue due to the high iron and zinc content of this waste. 相似文献
123.
C. O. Soares M. D. Carvalho M. E. Melo Jorge A. Gomes R. A. Silva C. M. Rangel M. I. da Silva Pereira 《Journal of Applied Electrochemistry》2012,42(5):325-332
LaNiO3 coatings on nickel-foam supports were prepared by brush painting. The electrochemical properties were investigated by cyclic
voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Comparative studies were performed with LaNiO3-pelleted electrodes. The roughness factors were determined by CV and found to be 5,208 ± 350 and 4,037 ± 250 for the pelleted
and coated electrodes, respectively. EIS measurements confirm the results obtained by CV. Values lower than 0.3 were calculated
for the morphology factors for both electrodes, indicating low electrochemical porosity. The experimental method used in this
work to synthesise the oxide coupled with the use of Ni foam as support has proved to be very effective in producing oxide
electrodes with surface areas higher than those referred to in relevant literature. 相似文献
124.
Alkylation of N‐vinylpyrrolidone using lithium diisopropylamide and bis(2‐bromoethyl) ether was carried out to obtain 3‐(2‐(2‐bromoethoxy)ethyl)‐1‐vinyl‐2‐pyrrolidone ( 2 ). The derivative 2 represents a versatile starting molecule for further modification via nucleophilic displacement yielding, for example, the bicyclic 2‐vinyl‐8‐oxa‐2‐azaspiro[4.5]decan‐1‐one ( 4 ) or the ammonium salt 3‐diethoxy‐N,N′‐((dimethylbenzyl)ammonium bromide)‐1‐vinyl‐2‐pyrrolidone ( 10 ). Via free radical polymerization of 4 and 10 , the corresponding homopolymers were obtained. Copolymerization of 4 and 10 with N,N′‐diethylacrylamide yielded water‐soluble materials. The thermosensitive solubility of copolymers poly[(2‐vinyl‐8‐oxa‐2‐azaspiro[4.5]decan‐1‐one)‐co‐(N,N′‐diethylacrylamide)] and poly[(3‐diethoxy‐N,N′‐((dimethylbenzyl)ammonium bromide)‐1‐vinyl‐2‐pyrrolidone)‐co‐(N‐vinylpyrrolidone)] in water was investigated. © 2015 Society of Chemical Industry 相似文献
125.
Rafael Mattos Deus Rosane Aparecida Gomes Battistelle Gustavo Henrique Ribeiro Silva 《Clean Technologies and Environmental Policy》2017,19(1):205-214
As achieving Brazil’s National Policy on Solid Waste-based goals effectively is not simple, there are alternatives such as intermunicipal cooperation by consortium or privatization. Therefore, this study aimed to evaluate the Greenhouse Gas emissions and energy use of six scenarios in two landfills contexts (private and consortium) for small municipalities (less than 100,000 inhabitants as per Brazilian standards) located in São Paulo, Brazil. Through the technique of scenario building and method of Waste Reduction Model was possible to obtain the total energy, the amount of carbon dioxide equivalent (CO2E) and carbon equivalent (CE) emissions. The best scenario integrates composting and recycling, reducing 72 % for CO2E and CE emissions, and saving about 410 % in energy. The landfill consortium will only take advantage, if the location is the most ideal as far as possible. Small municipalities that do not dispose their waste in landfills compatible with regulatory standards may seek for intermunicipal cooperation and adopt integrated waste-management programmes to reduce their environmental impacts. 相似文献
126.
Rajib Nayak James Gomes 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2010,85(1):59-76
BACKGROUND: A generalized methodology for the synthesis of a hybrid controller for affine systems using sequential adaptive networks (SAN) is presented. SAN consists of an assembly of neural networks that are ordered in a chronological sequence, with one network assigned to each sampling interval. Using a suitable process model based on oxygen metabolism and an a priori objective function, a hybrid control law is derived that can use online measurements and the states predicted by SAN for computing the desired control action. RESULTS: The performance of the SAN–hybrid controller is tested for simulated fed‐batch production of methionine for three different process conditions. Simulations assume that online measurements of dissolved oxygen (DO) concentration are available. The performance of the SAN–hybrid controller gave an NRMSE of ~10?4 in the absence of noise, ~10?3 and ~10?2 for ± 5% and ± 10% noise in the DO measurement and ~10?2 for parameter uncertainty when compared with the ideal model prediction. CONCLUSIONS: The observed performance for unmeasured state prediction and control implementation shows that the proposed SAN–hybrid controller can efficiently compute the manipulated variable required to maintain methionine production along the optimized trajectory for different conditions. The test results show that the SAN–hybrid controller can be used for online real‐time implementation in fed‐batch bioprocesses. Copyright © 2009 Society of Chemical Industry 相似文献
127.
Wirley Gonçalves Assunção Juliana Aparecida Delben Lucas Fernando Tabata Valentim Adelino Ricardo Barão Érica Alves Gomes 《Journal of Materials Engineering and Performance》2011,20(6):947-951
The passive fit between prosthesis and implant is a relevant factor for screw joint stability and treatment success. The aim
of this study was to evaluate the influence of vertical misfit in abutment-implant interface on preload maintenance of retention
screw of implant-supported crowns. The crowns were fabricated with different abutments and veneering materials and divided
into 5 groups (n = 12): Gold UCLA abutments cast in gold alloy veneered with ceramic (Group I) and resin (Group II), UCLA abutments cast in
titanium veneered with ceramic (Group III) and resin (Group IV), and zirconia abutments with ceramic veneering (Group V).
The crowns were attached to implants by gold retention screws with 35-N cm insertion torque. Specimens were submitted to mechanical
cycling up to 106 cycles. Measurements of detorque and vertical misfit in abutment-implant interface were performed before and after mechanical
cycling. ANOVA revealed statistically significant difference (P < 0.05) among groups for vertical misfit measured before and after mechanical cycling. The abutments cast in titanium exhibited
the highest misfit values. Pearson correlation test did not demonstrate significant correlation (P > 0.05) between vertical misfit and detorque value. It was concluded that vertical misfit did not influence torque maintenance
and the abutments cast in titanium exhibited the highest misfit values. 相似文献
128.
Water loss is a big challenge for water supply companies worldwide, and the Water Network Partitioning (WNP) is an excellent tool for water loss management–particularly in the current difficult economic and financial conditions. WNP is a recent research line and consists in dividing the water distribution network into smaller zones called District Metered Areas (DMAs) with one (or more, in exceptional cases) supply point, to reduce the network complexity and/or allow pressure management. Since there are several possible future scenarios, such as the water demand and/or the infrastructure degradation forecasts, which may have different impacts on the hydraulic behaviour, in this paper a computational application, based on an optimization model, is proposed to achieve a compromise between robustness required for the DMAs design (using a baseline scenario) and different decision makers’ options (using other scenarios with a lower “probability” of occurrence), to reduce the total cost. The objective function reflects the minimization of the squared deviations between the total cost of the DMAs design and the minimum cost for each scenario forecasted for the project plan, multiplied by the weight or “probability” of occurrence for each of the scenarios. The performance of the computational application is illustrated with a case study, and the results are encouraging. 相似文献
129.
130.
This paper adopts two perspectives. The first is a framing process aimed at defining and examining the conditions for adopting adaptive coastal governance. The second applies to relevant themes of changing coastal policy, central to the testing of adaptive coastal governance, namely cooperative science, risk-sensitive planning, socially fair insurance cover and effective ways to design, finance and engage with local communities over actual coastal change. We illuminate both missions through case studies in North Norfolk (England) and Portugal, all notably affected by coastal change. In England and Portugal, there is a broad understanding and acceptance of the likely effects of climate change. This recognition encourages debates over risk-averse planning, the design of proactive insurance cover, creative relocation of endangered property and new ways of predicting and paying for coastal adjustment. Yet, moving from a basic willingness to engage with coastal change to actual practices of landscape adjustment through such policy shifts is proving very difficult. In this research, we find that coastal landscapes are lived experiences, resigned acceptances of inevitable change and hopeful imaginings. Coastal management institutions are not geared to resolving this incompatibility and this paper explains why. 相似文献